18650電池市場應用化比較廣泛，目前主要流行的是18650鋰離子電池，其他種類的18650電池已經開始慢慢退出市場。那么18650鋰電池保護板怎么設計？這個18650鋰電池保護板不是固定的，基本是定制類的電池保護板。

鋰電池的保護功能通常由保護電路板和PTC等電流器件協同完成，保護板是由電子電路組成，在-40℃至+85℃的環境下時刻準確的監視電芯的電壓和充放回路的電流，及時控制電流回路的通斷;PTC在高溫環境下防止電池發生惡劣的損壞。

普通18650鋰電(dian)(dian)池保護(hu)板通常(chang)包括(kuo)控(kong)制IC、MOS開(kai)關(guan)、電(dian)(dian)阻、電(dian)(dian)容及(ji)輔助器件FUSE、PTC、NTC、ID、存儲器等。其(qi)中控(kong)制IC，在(zai)一切正常(chang)的情況下控(kong)制MOS開(kai)關(guan)導(dao)通，使電(dian)(dian)芯與(yu)外電(dian)(dian)路導(dao)通，而當(dang)電(dian)(dian)芯電(dian)(dian)壓(ya)或回路電(dian)(dian)流超過規定值(zhi)時，它立刻控(kong)制MOS開(kai)關(guan)關(guan)斷，保護(hu)電(dian)(dian)芯的安全。

在鋰電池保護板正常的情況下，Vdd為高電平，Vss，VM為低電平，DO、CO為高電平，當Vdd，Vss，VM任何一項參數變換時，DO或CO端的電平將發生變化。

1、正(zheng)常(chang)狀態

在正常(chang)(chang)狀(zhuang)態下電(dian)(dian)(dian)(dian)路中(zhong)N1的“CO”與“DO”腳(jiao)都輸出(chu)高電(dian)(dian)(dian)(dian)壓，兩個MOSFET都處于(yu)導(dao)(dao)通(tong)(tong)狀(zhuang)態，電(dian)(dian)(dian)(dian)池可以自(zi)由地進行(xing)充電(dian)(dian)(dian)(dian)和放電(dian)(dian)(dian)(dian)，由于(yu)MOSFET的導(dao)(dao)通(tong)(tong)阻(zu)抗很小(xiao)，通(tong)(tong)常(chang)(chang)小(xiao)于(yu)30毫歐，因此(ci)其導(dao)(dao)通(tong)(tong)電(dian)(dian)(dian)(dian)阻(zu)對(dui)電(dian)(dian)(dian)(dian)路的性(xing)能(neng)影(ying)響(xiang)很小(xiao)。此(ci)狀(zhuang)態下保護電(dian)(dian)(dian)(dian)路的消(xiao)耗(hao)電(dian)(dian)(dian)(dian)流(liu)為μA級，通(tong)(tong)常(chang)(chang)小(xiao)于(yu)7μA。

2、過充電保護

鋰離(li)子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)要求(qiu)的(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)方式為(wei)(wei)恒流/恒壓(ya)(ya)，在(zai)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)初期(qi)，為(wei)(wei)恒流充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，隨(sui)著充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)會上升(sheng)到4.2V(根(gen)據正(zheng)極(ji)材料不(bu)同(tong)，有(you)(you)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)要求(qiu)恒壓(ya)(ya)值為(wei)(wei)4.1V)，轉為(wei)(wei)恒壓(ya)(ya)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，直至電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流越來(lai)越小。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)在(zai)被充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程中，如果充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路失去控(kong)制，會使(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)超過(guo)4.2V后(hou)繼續恒流充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，此時(shi)(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)仍會繼續上升(sheng)，當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)被充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)至超過(guo)4.3V時(shi)(shi)(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)的(de)化學副反應將加劇(ju)，會導(dao)致電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)損壞或出現(xian)安全(quan)問題。在(zai)帶有(you)(you)保護(hu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)中，當控(kong)制IC檢測到電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)達到4.28V(該(gai)值由控(kong)制IC決定，不(bu)同(tong)的(de)IC有(you)(you)不(bu)同(tong)的(de)值)時(shi)(shi)(shi)(shi)，其“CO”腳(jiao)將由高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)轉變(bian)為(wei)(wei)零電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，使(shi)V2由導(dao)通(tong)轉為(wei)(wei)關(guan)斷，從而切斷了充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路，使(shi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器無法(fa)再(zai)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)進行(xing)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，起到過(guo)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)保護(hu)作用。而此時(shi)(shi)(shi)(shi)由于V2自帶的(de)體(ti)二(er)極(ji)管(guan)VD2的(de)存在(zai)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)可以通(tong)過(guo)該(gai)二(er)極(ji)管(guan)對外(wai)部(bu)負載進行(xing)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。在(zai)控(kong)制IC檢測到電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)超過(guo)4.28V至發出關(guan)斷V2信號之間，還有(you)(you)一段延時(shi)(shi)(shi)(shi)時(shi)(shi)(shi)(shi)間，該(gai)延時(shi)(shi)(shi)(shi)時(shi)(shi)(shi)(shi)間的(de)長(chang)短由C3決定，通(tong)常設為(wei)(wei)1秒左(zuo)右，以避免因(yin)干擾而造(zao)成誤判斷。

3、過放電(dian)保護

電(dian)(dian)(dian)(dian)(dian)池(chi)在(zai)(zai)對(dui)外部(bu)負載(zai)放(fang)電(dian)(dian)(dian)(dian)(dian)過(guo)(guo)程(cheng)中(zhong)(zhong)，其(qi)(qi)電(dian)(dian)(dian)(dian)(dian)壓會隨著放(fang)電(dian)(dian)(dian)(dian)(dian)過(guo)(guo)程(cheng)逐漸降(jiang)(jiang)低(di)，當(dang)電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓降(jiang)(jiang)至(zhi)2.5V時，其(qi)(qi)容量(liang)已被完全放(fang)光，此時如果讓電(dian)(dian)(dian)(dian)(dian)池(chi)繼(ji)續對(dui)負載(zai)放(fang)電(dian)(dian)(dian)(dian)(dian)，將(jiang)造成電(dian)(dian)(dian)(dian)(dian)池(chi)的永久性(xing)損壞。在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)池(chi)放(fang)電(dian)(dian)(dian)(dian)(dian)過(guo)(guo)程(cheng)中(zhong)(zhong)，當(dang)控(kong)(kong)制IC檢(jian)測(ce)到電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓低(di)于(yu)2.3V(該(gai)值由(you)(you)(you)控(kong)(kong)制IC決定，不同的IC有不同的值)時，其(qi)(qi)“DO”腳將(jiang)由(you)(you)(you)高電(dian)(dian)(dian)(dian)(dian)壓轉變為零(ling)電(dian)(dian)(dian)(dian)(dian)壓，使V1由(you)(you)(you)導通(tong)轉為關斷，從而切斷了(le)放(fang)電(dian)(dian)(dian)(dian)(dian)回路，使電(dian)(dian)(dian)(dian)(dian)池(chi)無法(fa)再對(dui)負載(zai)進行放(fang)電(dian)(dian)(dian)(dian)(dian)，起到過(guo)(guo)放(fang)電(dian)(dian)(dian)(dian)(dian)保護作用。而此時由(you)(you)(you)于(yu)V1自帶的體(ti)二極(ji)管VD1的存(cun)在(zai)(zai)，充(chong)電(dian)(dian)(dian)(dian)(dian)器可(ke)以通(tong)過(guo)(guo)該(gai)二極(ji)管對(dui)電(dian)(dian)(dian)(dian)(dian)池(chi)進行充(chong)電(dian)(dian)(dian)(dian)(dian)。由(you)(you)(you)于(yu)在(zai)(zai)過(guo)(guo)放(fang)電(dian)(dian)(dian)(dian)(dian)保護狀(zhuang)態(tai)下(xia)電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓不能再降(jiang)(jiang)低(di)，因此要求保護電(dian)(dian)(dian)(dian)(dian)路的消(xiao)耗(hao)電(dian)(dian)(dian)(dian)(dian)流極(ji)小(xiao)，此時控(kong)(kong)制IC會進入低(di)功(gong)耗(hao)狀(zhuang)態(tai)，整個保護電(dian)(dian)(dian)(dian)(dian)路耗(hao)電(dian)(dian)(dian)(dian)(dian)會小(xiao)于(yu)0.1μA。在(zai)(zai)控(kong)(kong)制IC檢(jian)測(ce)到電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓低(di)于(yu)2.3V至(zhi)發出關斷V1信(xin)號(hao)之間，也有一段延時時間，該(gai)延時時間的長短由(you)(you)(you)C3決定，通(tong)常設為100毫秒(miao)左右，以避免因干(gan)擾而造成誤判斷.

4、短路(lu)保護

電(dian)(dian)池在(zai)對負(fu)載放電(dian)(dian)過(guo)程中(zhong)，若回路電(dian)(dian)流大到使U>0.9V(該(gai)值由(you)控(kong)制(zhi)(zhi)IC決定，不(bu)(bu)(bu)同的(de)(de)IC有不(bu)(bu)(bu)同的(de)(de)值)時(shi)(shi)，控(kong)制(zhi)(zhi)IC則判斷(duan)為負(fu)載短(duan)(duan)路，其“DO”腳將迅速由(you)高(gao)電(dian)(dian)壓轉變(bian)為零電(dian)(dian)壓，使V1由(you)導通(tong)轉為關斷(duan)，從(cong)而切斷(duan)放電(dian)(dian)回路，起(qi)到短(duan)(duan)路保護(hu)(hu)作用(yong)。短(duan)(duan)路保護(hu)(hu)的(de)(de)延時(shi)(shi)時(shi)(shi)間極短(duan)(duan)，通(tong)常小于7微秒。其工作原(yuan)理與過(guo)電(dian)(dian)流保護(hu)(hu)類(lei)似，只是判斷(duan)方法不(bu)(bu)(bu)同，保護(hu)(hu)延時(shi)(shi)時(shi)(shi)間也(ye)不(bu)(bu)(bu)一樣。除了(le)控(kong)制(zhi)(zhi)IC外(wai)，電(dian)(dian)路中(zhong)還有一個(ge)重(zhong)要元件，就(jiu)是MOSFET，它(ta)在(zai)電(dian)(dian)路中(zhong)起(qi)著開關的(de)(de)作用(yong)，由(you)于它(ta)直接(jie)串接(jie)在(zai)電(dian)(dian)池與外(wai)部(bu)負(fu)載之間，因此(ci)它(ta)的(de)(de)導通(tong)阻抗對電(dian)(dian)池的(de)(de)性能有影(ying)響，當選用(yong)的(de)(de)MOSFET較好時(shi)(shi)，其導通(tong)阻抗很小，電(dian)(dian)池包(bao)的(de)(de)內阻就(jiu)小，帶載能力也(ye)強，在(zai)放電(dian)(dian)時(shi)(shi)其消耗的(de)(de)電(dian)(dian)能也(ye)少。

5、過電流保護

由于(yu)鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)(de)化學特性，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)生(sheng)產(chan)廠家規(gui)定(ding)了(le)其(qi)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)最大不(bu)能超過(guo)2C(C=電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)容量/小時(shi)(shi)(shi))，當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)超過(guo)2C電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)，將會(hui)導(dao)致(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)(de)永久性損壞或出現(xian)安全問題。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)在對負(fu)載正常(chang)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程中(zhong)，放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)在經過(guo)串聯(lian)的(de)(de)(de)(de)2個MOSFET時(shi)(shi)(shi)，由于(yu)MOSFET的(de)(de)(de)(de)導(dao)通(tong)(tong)阻抗(kang)，會(hui)在其(qi)兩端產(chan)生(sheng)一(yi)個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓，該(gai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓值(zhi)U=I*RDS*2，RDS為單(dan)個MOSFET導(dao)通(tong)(tong)阻抗(kang)，控(kong)制(zhi)(zhi)IC上的(de)(de)(de)(de)“V-”腳對該(gai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓值(zhi)進行檢(jian)測(ce)，若(ruo)負(fu)載因(yin)(yin)某種原因(yin)(yin)導(dao)致(zhi)異常(chang)，使回(hui)路電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)增大，當(dang)回(hui)路電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)大到(dao)使U>0.1V(該(gai)值(zhi)由控(kong)制(zhi)(zhi)IC決(jue)(jue)定(ding)，不(bu)同的(de)(de)(de)(de)IC有不(bu)同的(de)(de)(de)(de)值(zhi))時(shi)(shi)(shi)，其(qi)“DO”腳將由高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓轉變為零電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓，使V1由導(dao)通(tong)(tong)轉為關(guan)斷，從而切斷了(le)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回(hui)路，使回(hui)路中(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)為零，起到(dao)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)保(bao)(bao)護作用。在控(kong)制(zhi)(zhi)IC檢(jian)測(ce)到(dao)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)發生(sheng)至發出關(guan)斷V1信號之間，也(ye)有一(yi)段延時(shi)(shi)(shi)時(shi)(shi)(shi)間，該(gai)延時(shi)(shi)(shi)時(shi)(shi)(shi)間的(de)(de)(de)(de)長短(duan)由C3決(jue)(jue)定(ding)，通(tong)(tong)常(chang)為13毫秒左(zuo)右，以避免(mian)因(yin)(yin)干擾而造成誤判斷。在上述控(kong)制(zhi)(zhi)過(guo)程中(zhong)可知，其(qi)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)檢(jian)測(ce)值(zhi)大小不(bu)僅取決(jue)(jue)于(yu)控(kong)制(zhi)(zhi)IC的(de)(de)(de)(de)控(kong)制(zhi)(zhi)值(zhi)，還取決(jue)(jue)于(yu)MOSFET的(de)(de)(de)(de)導(dao)通(tong)(tong)阻抗(kang)，當(dang)MOSFET導(dao)通(tong)(tong)阻抗(kang)越(yue)大時(shi)(shi)(shi)，對同樣的(de)(de)(de)(de)控(kong)制(zhi)(zhi)IC，其(qi)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)保(bao)(bao)護值(zhi)越(yue)小。

18650鋰(li)電池保護板設計注意事項：

1、過充電檢(jian)出電壓：在通常(chang)狀態(tai)下，Vdd逐漸提升至(zhi)CO端由(you)高電平變為低電平時VDD-VSS間電壓。

2、過充(chong)電(dian)(dian)(dian)解(jie)除電(dian)(dian)(dian)壓(ya)：在(zai)充(chong)電(dian)(dian)(dian)狀態下，Vdd逐漸降低至CO端由低電(dian)(dian)(dian)平變為高電(dian)(dian)(dian)平時VDD-VSS間電(dian)(dian)(dian)壓(ya)。

3、過放(fang)電檢出電壓：通常(chang)狀(zhuang)態下，Vdd逐漸降低至DO端由高電平變為低電平時VDD-VSS間電壓。

4、過放電(dian)解除電(dian)壓：在過放電(dian)狀態下，Vdd逐漸上升到DO端由(you)低電(dian)平變(bian)為高(gao)電(dian)平時(shi)VDD-VSS間電(dian)壓。

5、過電(dian)(dian)流1檢出(chu)電(dian)(dian)壓：在(zai)通常狀態(tai)下，VM逐漸升至DO由高電(dian)(dian)平變為低電(dian)(dian)平時VM-VSS間電(dian)(dian)壓。

6、過電流2檢(jian)出電壓：在通常狀(zhuang)態(tai)下，VM從OV起以1ms以上4ms以下的速度升到DO端由高電平變為低電平時VM-VSS間電壓。

7、負載短(duan)路(lu)檢出電(dian)壓(ya)：在(zai)通常狀(zhuang)態下，VM以OV起以1μS以上(shang)50μS以下的速度(du)升至DO端由高電(dian)平變為低電(dian)平時(shi)VM-VSS間電(dian)壓(ya)。

8、充電(dian)器檢出電(dian)壓(ya)：在過(guo)放(fang)電(dian)狀態下，VM以OV逐漸下降(jiang)至(zhi)DO由(you)低電(dian)平變為(wei)變為(wei)高(gao)電(dian)平時(shi)VM-VSS間電(dian)壓(ya)。

9、通(tong)常(chang)(chang)工作時消耗電流：在通(tong)常(chang)(chang)狀態下，流以VDD端子的電流(IDD)即為通(tong)常(chang)(chang)工作時消耗電流。

10、過放(fang)電消耗電流(liu)：在放(fang)電狀態(tai)下，流(liu)經VDD端子(zi)的電流(liu)(IDD)即為(wei)過流(liu)放(fang)電消耗電流(liu)。